text:
Best way of learning the aviation alphabet?
I want to learn the aviation alphabet, and when searching the Internet on how to, I see a plethora of approaches, so I thought of asking here!
If it's primarily opinion based, let me know.

The best way is probably to start off knowing the marine alphabet.  Then it's trivial!

The marine alphabet? Never heard of that... Why do you think that this will help @TobySpeight?

If it's anything like the Brooklyn Alphabet it's unprintable @gsamaras.

The marine radio alphabet is the NATO phonetic alphabet, so it's identical to the aviation radio alphabet.  So if you already sail or otherwise use the sea, there's nothing new to learn (but some different pro-words, of course).

Whatever you do, don't watch American cop shows on TV. They use a different phonetic alphabet.

I had watched "Psych", I don't remember if they used any of it! :O But, luckily my father is an avionics technician, so I think that my experiences relevant to that are good based, +1.

How can I learn French? Don't watch Spanish telenovelas. True, but not particularly helpful.

Actually, it's a bit more helpful than that - it's worth knowing which spelling alphabets are the same as ICAO and which are not.  If expanded from something that should be a comment into a full answer, it could be valuable here.

Practice, practice...  There is no shortcut or substitute for repetition.  Read off signs and license plates while driving.

I name the items in bathroom while enjoying my time there.... They will run out at some point though, so thanks for the tip @MichaelHall.

Sing it like in grade school! Just don't injure your tongue at "limamikenovemberoscarpapa." :P

I never really learnt the real alphabets @TomMcW, not the English, not the German, not the Italian and not the Greek, so I think I should be skeptical about this, since it also invokes some hazards as you mention! ;)

@gsamaras My comment is facetious of course.  In the US there's a particular tune grade school kids are taught to learn the alphabet. Most of the tune puts each letter on a quarter note, but LMNOP are on 16th notes. No problem to sing "elemenohpee" on sixteenth notes, but if you try singing the phonetic alphabet to that tune you get hilarious results.  That tune gets so ingrained in our heads that one thing I've seen police do in a sobriety check is to ask you to simply recite the alphabet without singing it. The letters and the tune are so well associated that intoxicated people have trouble

Of course if you recite the ICAO alphabet to the police they will have no idea what you're doing. They use a completely different phonetic alphabet

APCO 2 and NATO aren't entirely different.  They both use "Victor" and "X-Ray".

@TomMcW, are you telling me that if a cop said to you - "George Tom Frank Ocean" you would have no idea what he was talking about?!  ;)

Mnemonic poem for memorizing the NATO alphabet

I am not sure if it is the easiest way. But the quickest and most permanent way is to join the military. You will know it in no time. Or, else...  ****

I just know it by reading it alot

Presuming you're referring to the ICAO Alphabet* , (alpha, bravo, charlie, delta, echo, etc.) the easiest way (in my experience, from learning it as a disambiguator for phone work) is repetition, same way you learned the alphabet as a child, or the same way you'd memorize a poem.  Get a written list of the letter names, read them through several times a day, and over time, start reciting without reading.
Do this several times a day for a week, you'll be close if not there.  A second week and you should start to think in phonetic alphabet.  A third week and you'll wonder why everyone doesn't think in phonetic alphabet.
*corrected from comments, originally International Phonetic Alphabet, which is a whole different thing.

"Did you just assume my" alphabet knowledge? Kidding, even though I don't really know the real alphabet, so I'd better learn the useful one! :)

Once you can recite it in order, practise by spelling out (in your head, if you're not alone) things you see in daily life.  For example, if you drive, spell out each car number plate you follow.  You might need a different source of letters if you're in a country where the plates are all-numeric, but I'm sure you can use some imagination...

I think that I just figured out the next pick-up line for a girl.. "Wanna hear your name in Aviation Alphabet?"... Damn, I did that already for the lady I met on Saturday, got half of them correct, I think! :)

Billboards and road signs work as well as licence plates.

@TobySpeight - that's exactly what I did! I did it so much, I still read them that way now. Even when I don't want to... :/

The problem with billboards and road signs is that, while you'll pick up on echo and alpha pretty quick, it'll take you a while to learn juliet, quebec, x-ray and zulu...

I worked in a call centre and used it constantly for 8 hours a day to clarify details on terrible phone lines.

@burgi That's exactly my story.  People around me were using all sorts of random "sound-alikes" and still not clear -- so I memorized the real one.

(source: i0.wp.com)
Study like it's schoolwork!
I've found that quizzing yourself in a similar way to studying for a test is the best way to learn. I've had to learn a few different alphabets for different reasons, but there's always good resources online. I'd recommend two tests that I always give to beginners.

Beginner Quiz: https://www.sporcle.com/games/g/alpha_en
Intermediate Quiz: https://abg.ninja/alphabet

Ignoring the childish UI, these are actually great ways. Begin with the first link, and type in all of the letters that you know. This will very quickly show you which ones you know, and which you don't. Once you've figured out the ones you don't know, check a chart, attempt to memorize them, and try the test again. Rinse and repeat until you've memorized it fully, and can do it an hour after looking at the chart (so the information isn't remembered solely for being fresh in your mind).
After you've done this, use the second link I sent you to improve your usage, and to string multiple letters together. Continue until you're comfortable.
It's incredibly helpful to read the letters out loud while doing these tests.

That seems like a good idea. However, "The webpage at https://www.sporcle.com/games/g/alpha_en might be temporarily down or it may have moved permanently to a new web address.". In any case, the second one works, so +1.

@gsamaras Glad I could help - webpage is there for me. Make sure you copy the entire link, including the "https://" and "www."

One thing.  It is pronounced KAY-beck, not kwee-BECK.

The best way is by listening and having software score you.  I wrote just such a page here:
http://www.qa76.net/npa
It's free.  No gimicks.  It's just something I wrote for fun because I couldn't find anything like it.
It has a leaderboard.  You can speed it up or slow it down.  You can ask for short or long messages.
I like to use it during boring meetings at work.  The background interference from the meeting makes it more challenging!
Use it in good health!

My favorite method for memorizing that kind of stuff is to create flash cards with a picture that can be associated with the word. You might have to use your imagination for find a suitable image for each letter, but once you do, the memorization efficiency goes way up.
Another option is to make flash cards with the letter and its phonetic word in a huge font so it takes up an entire page.  You will find you are able to recall the "image" of the word more easily than just the information itself.  I use that method for memorizing operating limitations where it's just a numerical value you have to store in your head.

I have photographic memory, +1

Off topic, but there is a neat method to memorize Morse code if you're so inclined.  You create a list of phrases with a cadence that matches the letter.and memorize the phrases.  For A, I used "A Chooo" dot dash... B is "Brown Choc-co-late" dash dot dot dot... C is "Charlie Charlie"  dash dot dash dot... D is "Dag nabbit!"  dash dot dot... E is "Eh"  dot... F is "Funny Handle" dot dot dash dot.   and so on.  Not that much practical use to be sure.

Make drawings (it doesn't matter how good you can draw). Use whatever comes to your mind first. For example: for Charly I think of Charly Brown. For Mike its another comic figure called Mike, but unlike Charly he is very tall, so these two side by side look very funny. They together (funny view remember) are visiting Quebec in November...
... where they meet Romeo and Juliet who are dancing Tango.
Take just a few at a time. Make each of them tell a little story. Stick them where you can see them several times a day. Bathroom for example.
If your brain has something to visualize its more likely that you will remember.

Thank you story teller!

Very similar to the methods my wife used to use to teach American 8th graders some Spanish.

I can recommend the (free) site http://radioalphabet.com/, specifically the Flash Cards tab. It provides you with a word, listed vertically with an input box besides each letter, and requires you to write the second and third letter of the word for each letter (which are unique amongst the words). It then automatically jumps to the next box, allowing you to practice quickly recalling the words for each letter.
After you have used it for a little, the Statistics tab provides you with hit and miss rates for each letter, so you can know which ones to focus on memorizing. I personally schedule repetitions in my calendar, using the principle of spaced repetition learning mentioned in insysions answer, so I increase the time until next repetition if I get everything right.

That's super!!!

@gsamaras: Glad you like it. :-D

What works for me (and by no means suggests optimality) is having a card close on hand (in this case in our fire truck) with the names in alphabetical order.  While talking on the radio it’s easy to refer to the card when necessary, and having read the words out aloud in context they tend to stick.  That said, we’re volunteers and don’t get a great deal of practice on the radio so a different approach might be more appropriate to ‘frequent fliers’ who are using the alphabet daily.

When you say “names”, are you referring to the police and emergency services phonetic  alphabet. It is not the same as the FAA/IAO/NATO alphabet.

NATO is what we use (NZ), it may vary by jurisdiction.  I’m aware of the APCO alphabet but to the best of my knowledge it’s more or less obsolete, possibly to streamline inter-agency operations.

I had the same problem. The easiest way to me to remember all the letters is with the car plates. It's fun and also keeps you practice the alphabet without a specific order, that's important too.

This answer could be viewed as much like this other answer to the same question, but taken one step further.
The other answer said

Make drawings (it doesn't matter how good you can draw). Use whatever
comes to your mind first. For example: for Charly I think of Charly
Brown.

Well, when I was a kid in middle school, and already quite obsessed with aviation, I used the phonetic alphabet to make my own personal secret written alphabet.  For example, "Charlie" was a simple zig-zag squiggle that resembled the two pointed ears of a cat, because a member of my extended family had a cat named Charlie.  "Mike" was a vertical line with a dot on top, like a lower-case letter "i" but without the space below the dot, resembling a hand-held microphone like a singer might use.  "Alpha" was associated with "Alpha Romeo" and was depicted by a very simplified representation of some feature of a car (it happened to be a steering wheel, represented by a circle with a slash through it.)  And so on and so forth-- some of the codes were downright silly, but that didn't matter, because they were still memorable to me for one reason or another.  The symbols were so simply drawn that a) they could be drawn just about as fast as the actual normal letters, and b) anyone not in on the "secret" that this was all based on the phonetic alphabet, would never guess what object they were supposed to be depicting, even in cases where the actual object would have been familiar to almost anyone (unlike the specific cat named Charlie.)  The harder the symbols are for anyone else to figure out, the better (after all, it's supposed to be a code), so long as there's just enough there to jog your memory sufficiently.
(But at the end of the day, it is still just a simple substitution code, so don't entrust to it any secrets that you truly hope to take to your deathbed!  Of course, tricks like using phonetic spellings rather than actual spellings, omitting some of the vowels from some words, etc, will help address this issue.)
So, invent your own secret personal written alphabet based on these little esoteric hieroglyphics that are keyed to the phonetic alphabet, and practice spelling our whatever strikes your fancy-- your name, lists of the names of your friends and foes, and so on and so forth.  A great way to practice the phonetic alphabet instead of working on your actual class work like you are supposed to be doing--

Spaced repetition learning. E.g. https://www.memrise.com/course/31682/nato-alphabet-3/

It's best to explain further rather than just providing a link, in case the link is inaccessible.

I disagree that this is a link-only answer. The fundamental answer is "use spaced repetition", a well-known learning technique which one can easily find information about once they know that's what they're looking for. A detailed description of that general learning technique is probably out of scope for a site about airplane stuff.


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Are there legal limits associated with the use of the autopilot in the US?
A lot of new avionics basically fly small planes for you. Looking at a Beechcraft with a pretty cool glass cockpit, it claims to do everything for you except within 50 feet of the ground. Basically you takeoff and land and nothing else according to the advertising.
I'm planning on doing more than that, but it made me curious, is the "within 50 feet of the ground" non-autopilot part because it's a legal requirement or because it's just the trickiest part and they don't want to deal with that?
Is there a legal requirement in the US for part of the flight to be piloted manually, whether that be percentage or just takeoff and landing or is that just the hardest part to automate? If so, can it be remotely piloted?

I'm confused. Do you mean to say that the autopilot does everything except when you're within 50ft of the ground?

What does "do everything for you" mean? Even if you're using automation, you still have to tell the computer what you want it to do. The output can only be as good as its input. Telling the automation what to do (and knowing how much automation to use when) is very much part of the skill of piloting a suitably equipped aircraft; you're just manipulating higher level controls.

This varies based on if you are VFR or IFR certified.
Basic currency requirements for general aviation flying under part 91 which I presume is the target of this question. The comments to the answer outline the commercial implications, can be found in

§61.57   Recent flight experience: Pilot in command.
(a) General experience. (1) Except as provided in paragraph (e) of
  this section, no person may act as a pilot in command of an aircraft
  carrying passengers or of an aircraft certificated for more than one
  pilot flight crewmember unless that person has made at least three
  takeoffs and three landings within the preceding 90 days, and—
(i) The person acted as the sole manipulator of the flight controls;
  and
(ii) The required takeoffs and landings were performed in an aircraft
  of the same category, class, and type (if a type rating is required),
  and, if the aircraft to be flown is an airplane with a tailwheel, the
  takeoffs and landings must have been made to a full stop in an
  airplane with a tailwheel.
.... [read on for IFR and night currency]

However the FAA actually views using the auto-pilot as manipulating the controls. You can find the full legal interpretation here. But in short,

The FAA considers a pilot's use and management of the autopilot to be
  the equivalent of manipulating the controls, just as one manages other
  flight control systems, such as trim or a yaw dampener. The autopilot
  system's sophistication does not affect a pilot's responsibility to
  manipulate and manage all control systems, including an autopilot,
  appropriately. Therefore, a pilot may log PIC flight time as the sole
  manipulator of the controls for the time in which he or she engages an
  autopilot.

With that in mind you can maintain your currency using only auto-pilot and in theory if your plane and the desired airport was equipped for auto-land (which, as far as I know, no GA planes are) you could maintain your currency without physically manipulating the yoke aside from takeoff and climb to autopilot altitude. So no there is no legal obligation to physically touch the controls to maintain currency if your plane is capable of some kind of completely programmable flight (I don't think any are currently).
There is however one notable exception to this regulation. On an IFR checkride you must fly a manual approach,

From the ACS...
• The applicant must accomplish at least two nonprecision approaches in simulated or actual weather conditions.

At least one must be flown without the use of autopilot and without
  the assistance of radar vectors. The yaw damper and flight director
  are not considered parts of the autopilot for purposes of this Task.

It claims to do everything for you within 50 feet of the ground.

This is a bit misleading. First off, most, if not all GA planes lack auto-throttle so power management is in the hands of the pilot and is fully manual in most cases. Some more modern airplanes like the DA-42 have FADEC which loops prop and throttle controls to one lever minimizing but not eliminating manual control.
There are lots of autopilots out there and function varies heavily: some only have a single axis (heading hold and adjust capability). Some have 2 axes which can hold altitude and headings and some which have the ability to follow GPS courses, fly approaches down to different minimums etc. It should be noted that some units can be set to create situations that can stall the aircraft or otherwise put it in a dangerous flight scenario, the auto in autopilot does not mean absolute protection or full automation.

If so, can it be remotely piloted?

This is actually a completely separate question if you are asking "do I need to physically be inside the aircraft" i.e. "can I maintain currency with a drone if it's properly equipped". I don't think the FAA has fully fledged regulations on this yet. If by remote you mean by use of autopilot, see above.

IIRC on the Mythbusters episode about someone "talking the plane down", the vastly easier option was for them to just push the "autopilot" button, which would land the plane on its own.

There is no such thing as an "autopilot" button. Autopilots have many modes which are activated though different buttons. There is also no "auto-land" button that must also be set up and not every plane or airport has the facilities or equipment required for that. APR mode will get you close to the runway if the rest of the instruments are properly set up but will not land the aircraft.

For part 121,  there are regulations. See 14 CFR 121.579. https://www.law.cornell.edu/cfr/text/14/121.579

The pilot must abide by the limitations of the aircraft.  The Pilot Operating Handbook and supplements will include limitations pertaining to when a particular autopilot may be used.
For example, a Garmin autopilot may have a minimum engagement speed of 70 KIAS.  Notwithstanding other limitations and a FAR pertaining to careless and reckless operations, using the autopilot for takeoff or landing would not be approved.

70 KIAS is far below liftoff or touchdown speeds for your typical aircraft.

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Why would the U2 descend more quickly with its engine on than off?
I was talking to someone who got to fly in the U2. He mentioned that the pilot said that a descent from 70k' would take two hours with the engine working, or three hours without.
I have every reason to believe this source, but I can't see why it would be true that the plane can descend more quickly with an operational engine. Any usage of the engine, unless it's providing reverse thrust, would add energy to the system, and any added energy will increase flight time.
Anyone have any insight?

Just spitballin', but one guess would be a pitch attitude limitation that prevents you from diving beyond a certain nose-down angle, so that at the maximum dive angle you can fly at, you can't achieve the max dive speed, and get a higher descent rate, without some thrust on.

According to Wikipedia, the U-2 has a glide ratio of 23:1. With engine out and high up, the only thing you can do is glide, and without engines you slow down. So it can take a while to get on the ground. With engines, you can climb at 9,000 feet per minute. May not be able to descend quite that fast (safely) but certainly much faster than when gliding. Though 2 hours or 3 hours sounds pretty long to me.

@JohnK that has a certain ludicrous sense to it. Although I wonder why there'd be a shallow max nose-down angle, considering the steep angle of initial climb-out.

This article seems to contradict the basic premises of this question. I.e to descend one pulls throttle to idle and you’re at pattern altitude in 40 minutes.  http://www.barryschiff.com/high_flight.htm

That doesn't make any sense to me at all,

@KennSebesta  Revised comment… Above 65k ft this aircraft is flown within its coffin-corner: stalling speed = limiting mach-buffet speed. The aircraft can be difficult flown by hand; flight systems behest the pilot.  On descent, these critical limiting flight velocity boundaries widen; a nose-down power-off descent at a steeper glide path is possible, thereby allowing shortened descent times.  The full power-on steep angle ascent is easily velocity managed, but descent velocity management is critical to prevent overspeed. Once again, under certain conditions, flight systems behest the pilot.

@quietflyer Your point is well taken.  Thank you!  A brain-o-graphical error corrected and hopefully clarified through my revised comment.

Would love to know why people would downvote the lived experience of a man who got to fly to >70k'. If you don't believe he's remembering correctly (extremely unlikely, but anything's possible), then say so. If you have specific knowledge of the U2 which contradicts what he was told by his pilot, please share that as well. Otherwise, as a glider pilot I am really curious why the pilot of one of the world's highest-performance gliders would report needing more time to come down without the engine than with.

@mannasse.. , Glide ratio specifications assume that you are "gliding" at L/D max AOA, where drag is the lowest. They are not applicable to a situation where you are trying to achieve as high a descent rate as possible. Not to mention the existence (the necessity), of speed brakes and other drag-inducing devices on any such aircraft).

@Kenn, not to downvote the experience .... , but my guess is that either there was a message translation, transmission or memory error somewhere, or the pilot was ribbing the gentleman who relayed this to you. Second hand information is always a bit more suspect, but when it seems to violate common sense ... It just might be, for example, that the pilot was speaking about a scenario where the engine froze due to oil starvation, and was no longer producing hydraulic or electric power. In that case no drag-inducing devices (like speed brakes, landing gear, etc), could be activated...

From this the engine was used to extend "everything" to create drag and was only kept at idle power. 23 minutes was the typical descent time, not two hours, which went up to an hour if engine power couldn't get drag creating protuberances extended.

For descent almost everything possible on the aircraft is extended. The throttle to idle, lowered landing gear, raised spoilers and flaps in the gust-up configuration and extended fuselage-mounted speed brakes. Once stable on descent, the rate is close to 3,000 fpm. A speed of Mach 0.715 is used to 53,000 ft., when a speed of 160 kt. is established. In the case of either an engine or electrical failure, with the aircraft descending clean, it could easily take longer than an hour to descend from altitude.

From the flight manual (1967 edition) we learn that

A glide from 70,000 feet to sea level will take about 73 minutes and from 35.000 feet to sea level will take about 48 minutes.

and, in section III (emergency procedures):

If it becomes necessary to reach lower altitudes in the minimum time, the descent can be made faster by remaining in a banked spiral and increasing the speed to maximum allowable IAS limits. The bank angle and stick forces should be varied as necessary
to avoid exceedig G limits and to stay out of heavy high speed buffet. The only disadvantage is an increase in general roughness. Shutting the engine down will increase the rate of descent but may result in windshield and canopy frosting.

Section VI warns that

The descent in the high altiude area from 75,000 feet down to 70,000 feet is slow. The engine power, even on minimum flow, is still considerable at this altitude and the drag items do not produce much drag at indicated airspeeds at 90 to 100 knots.

Now I wonder which exact type of U-2 your friend has experience in since those points in the flight manual all contradict his statement.
If even the landing gear should be lowered in order to add some drag, it is obvious that the U-2 needs all the help it can get to descend quickly. There is a hydraulic accumulator and a battery of 35 Ah, so even a power loss will still allow to deflect the drag items. However, without sustained hydraulic pressure, the speed brakes will be slowly pushed in by the airstream, so a power-off descent, while subtracting the still considerable idle thrust, will also cut speedbrake drag.
Again section VI:

The airplane has conventional speed brakes which are moderately effective. Their primary use is as a drag producing device for descent, approach and landing.  […]  The speed brakes are fully variable and can be set at any desired position. In some cases they will creep closed from an intemediate position after a period of time. They cannot creep closed from the fully extended position if the switch is left in the extended position.

The only reason for a slower descent with power off is the closing of the speed brakes from loss of hydraulic pressure. This will become more effective at lower altitudes when Mach limits allow to fly at an IAS of 220 knots (gust control to faired) rsp. 240 knots (gust control to gust). Still, the manual advises to shut the engine down in order to increase the sink rate. Windmilling should still create some hydraulic pressure, but the manual does not go into details here.

Not sure that the U-2 has powered flight controls. This article suggests it does not: "The controls provide feather light control response at operational altitude. However, at lower altitudes, the higher air density and lack of a power assisted control system makes the aircraft very difficult to fly. Control inputs must be extreme to achieve the desired response..."

This makes a lot of sense, and I'm starting to see how a pilot could hand-wavingly refer to "two hours" vs. "three hours". I feel like an engine-out scenario, where there is loss of control of speed brakes, could absolutely tip the scales in favor of a slower descent. And an extra +1 for digging up the U2 flight manual.

More Ah on the battery might help, perhaps with a twirling device in front to charge it even more, no?

@RobertDiGiovanni As I understand it, loss of hydraulic pressure is more important because you lose control of the speed brakes. Electricity is needed for the instruments and radio but not flight-essential stuff. And there is a big twirling device inside the plane: The shut-down engine will idle from dynamic pressure with RPM between single digits and 20% of full thrust, depending on airspeed and density.

@PeterKämpf    In preparation of a separate yet similar answer, the indication from the flight manual is that the minimum power setting is to idle, while no power/power off is due to an engine issue.  If not seized, windmilling of the engine will still produce hydraulic power and may sufficiently operate the battery charging generator.

Would love to know what the plan is if you lose cabin pressure then :D

@Cloud The is a nitrogen bottle to keep the canopy seal pressurized in case of engine shutdown. So in regular operations an engine shutdown will keep the cabin pressurized long enough to descend. All bets are off, of course, when a damage opens a gaping hole in the cockpit walls. Then only the space suit of the pilot will keep him alive.

"descent from 70k would take 2 hours with the engine working, and 3 hours without"

As with many learning aides, or acronyms, this seems so crazy one has to remember it.
The foundation for the "myth" can be found in here, in a reference provided by @quietflyer, paragraph 4, section "on final approach".  Clean, at 109 knots Vbg, the U2 has a glide ratio of 28:1.  "Normal" descent is 37 Nm for every 10000 feet, roughly 2/3 clean glide ratio.
For those proposing use of thrust to descend faster (sort of a diving version of Vy), while theoretically correct, generally runs up against Vne in reality.  Rate of descent is determined not only by speed, but also by angle of descent.

where speed is limiting, greatest angle of descent gives the greatest rate of descent.

So, as we all do with flaps, spoilers etc., increasing drag increases angle of descent.
Apparently, in this case, the increase in drag is greater than the increase in thrust by leaving the engine on (at idle to operate the drag systems).  The angle of descent is lower clean with the engine off, because net drag (Dc) < (Dd-T) "dirty"/engine at idle.

Many aircraft have a significantly higher allowable airspeed clean, compared with flaps down.  Here, descending at a higher airspeed may produce a higher rate of descent, but gravity will provide all the "thrust" that is needed.

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text:
What is the FAA definition of a "flight"?
For the purposes of aeronautical experience for glider ratings, the FAA requires a certain number of "flights". However, I cannot find a definition of "flight" in the federal register: https://www.ecfr.gov/current/title-14/chapter-I/subchapter-A/part-1.
I'm looking for a legal definition which meets the obvious need that a winch or tow takeoff be considered a "flight". Furthermore, I'd like a definition which gives clarity to the following edge cases (as well as others not mentioned below):

If I do an aborted takeoff after being wheels up, is that a flight?
If, in a self-launching glider, I take-off and land with never having turned the engine off, is that a flight?
If I do a touch-and-go with a self-launching glider, is that a flight?

It is not in the best interest of the FAA to provide clarity as to the answers to your questions.   Confusion works better for them.  Related: https://aviation.stackexchange.com/a/55829/34686

I can't agree. The FAA can't (well, at least shouldn't) have a hard requirement without even a definition. Otherwise, a DPE could reject a candidate arbitrarily. This isn't a question of +- a few percent: if in two hours I did 20 touch-and-gos in a self-launching glider it shouldn't be debatable whether I'd satisfied either 1% or 20% of the CDX requirement for 100 "flights".

FAR 1.1 defines "flight time" as

(1) Pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing; or

(2) For a glider without self-launch capability, pilot time that commences when the glider is towed for the purpose of flight and ends when the glider comes to rest after landing.

I'd infer from that definition that one "flight" starts and ends at those events.  I can't tell you that's certainly right, but I'd think that an interpretation contrary to that (i.e. that a 2-hour block of time in which multiple touch-and-go's were conducted equates to multiple "flights") would probably be an uphill battle.
In that light, I think each of the first two examples in the question both constitute "one flight" since in each case, movement started (once) and the aircraft came to rest (once) after landing, and that "the flight" that entails a series of touch & go's is also "one flight" since the aircraft only "comes to rest after landing" once.
EDIT: On further reflection... for question #2, it's "a flight," but is it a flight in a glider?  If you never turned the engine off, that ("in a glider") part becomes more dubious.  And for that matter, #3 being "one flight" gets the same question... if the motor ran the whole time, not just during the T&G, is the whole thing even one "flight in a glider" at all?
That "in a glider" angle on it all is something that a CFIG can address better than I can.

Does this mean that you should avoid stopping while taxiing to your final destination at the airport if you can taxi continuously without creating any safety risk, because the first time you stop, you can no longer count time?

@Someone, no - that is not what it means.

@Someone: In the airline world, your flight time stops when we're at the gate & the doors open, i.e. with the parking brake set & the engines off.  That is "coming to rest" after landing.  Time still runs even though the aircraft may stop during taxi many times between landing and the gate. Your logged "flight time" certainly does not end at the moment that the wheels stop rolling.  If the FAA wanted it like that, then we wouldn't log time the way that we do. FAR 1.1 doesn't end your flight time merely at your first moment being stationary after a landing.

@RalphJ good answer. I would add, however, that the glider is an FAA certification category, so engine or not, if an aircraft certified as a glider leaves the ground, then it's flying and there must have been, at least, one flight.

@KennSebesta Yeah, I can't speak to how use of the motor full-time affects the count of flights "in a glider" or not. If you're off the ground, as in the 1st question, that has to be a flight.  I could see, though, a DPE looking askance if very many of ones "flights" were just a few seconds long & a few feet off the ground, only. How much does one really get out of the 23rd "simulated rope break"?


text:
Why was the Sikorsky Firefly built but never flown?
Sikorsky Firefly is the electric helicopter that has been built but never flown. How do such histories happen?
If the design looked so unsafe that there was not enough courage of trying, why this was not discovered much earlier? If they changed they mind, lost the investor, why not to try at least once anyway if there is already a machine standing ready to power up? Is there any certification for even the first ever flight a prototype may fail to pass?
Stories like "a single prototype was tested but not more ordered" look much more logical (they did not like it after the tests).
What are the most usual reasons behind the "built, never flown" histories?

Just a guess: Inspired by Tesla, Management wanted an electric vehicle, too. That worked well until first flight: Unlike the press, physics cannot be cheated, even with massive marketing budgets.

The director of Sikorsky Innovations Chris Van Buiten called it a

technology demonstrator and research platform that will let us explore the technology, partnerships and technical collaboration...

On 2010 July 29 Verticalmag.com reported

First flight is anticipated later this year, upon completion of ground tests and safety of flight reviews in accordance with Sikorsky standard practice for all aircraft programs.

It vanished from the news a few months later.
Ten years later, it may be hard to get someone from Sikorsky Innovations to speak on the record about Firefly's abandonment, something that the company might consider embarrassing.  But it seems likely that some ground tests failed (cooling? software?), and either the partnerships with the companies providing the batteries, motor, software, etc., weren't important enough to the company (or its owner, Lockheed Martin?) to address those defects, or its other projects became more important.

Also, actual airborne tests require a lot more testing and certification, so it's not just a simple matter of taking a prototype and sticking a test pilot in. I guess they didn't deem it worth the investment.

Looks like, indeed, the company has a "safety of flight reviews" after the prototype has been built and not just after the drawing is finished.


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How are aircraft depainted?
There are several questions about livery changes and livery in general on this website. Yet, I fail to find information about paint removal.
As a routine maintenance for an airframe that can live for up to 30 years, livery is redone several time as explained here. When changing painting, it should be preferable to remove the old one (I'm mostly thinking about weight as a big airliners has a lot a surface to paint). Moreover, I imagine that for military aircraft changing their operation theater, paint must be redone to adapt camouflage, and thus accumulating many layers of paint may have consequences.
Given material and other aviation-specific constraints, I also imagine there are special techniques to handle any intervention on the airframe.
Is this paint removal done and if so, how?

Tangentially related: https://aviation.stackexchange.com/questions/14500/why-is-most-aircraft-livery-painted-rather-than-vinyled

@Hosch250, the air may be the same color, but the ground isn't, and military airplanes tend to spend most of their time on or very close to the ground.

@Hosch250 See this one: What is the dark spot visible below the cockpit on A-10s?

@Hosch250 The US midwest is, proportionally, only a very small part of the world.

Paint stripper. Lots of paint stripper.
(originally I said thinner, but I have been corrected, it's more accurately called stripper)
Seriously though, it's actually not too different to other things that you paint. You need to spray on paint stripper. But, just like when painting the aircraft, it's imperative that you cover up all the delicate systems on the aircraft fuselage.
See here:

Also, I think it would be rare to paint a new livery over and existing one without first removing the old paint (maybe only if you were just changing small details), because covering an aircraft in paint weighs A LOT. For a 747 or 777 sized aircraft the paint job can weigh over 1000lbs
Carrying that around costs fuel and fuel costs a lot!

Welcome to Aviation.SE! Nice first contribution, I hope you stick around.

When my plane was repainted in fall in 2018, paint stripper was used. Hydrogen peroxide based, it took everything off. http://www.crossroadsfencing.com/airplane/painting%20pics/IMG_0200.JPG  After sitting overnight, the plane is rinsed and the wastewater collected in barrels to be shipped off and processed somehow.  Some areas needed a 2nd application to get down to bare aluminum  http://www.crossroadsfencing.com/airplane/painting%20pics/IMG_0202.JPG

What is paint thinner? Organic solvent? What is it in particular (or just some examples) - compounds? Are there special ones for aircraft?

Paint thinner is mineral spirits (Stoddard solvent) which may have been washed, i.e. recycled. Paint stripper is an organic solvent mixed with wax to slow evaporation; the solvent penetrates the paint and causes bubbling as it evaporates lifting the paint. Methylene chloride and NMP are common. The stripper in the video is a combination of solvent and caustic compounds such as lye that actually dissolve cured paint. You won't find them at the local hardware store because they also dissolve the lignum in wood, but they are sold to shipyards, and I assume, aircraft painters.

Paint thinner doesn't make paint melt off like that.  The video says "thinner", but that's not what's happening.  As Matthew points out, it's some type of paint stripper.  Just waned to reiterate that it is not just thinner.  Answer should be edited.

If I had to guess the stuff they are using in that video is called, "Aircraft Stripper". IN cycling, if you paint your frame, you can remove baked on coatings with it as well. For a consumer, you can buy small jugs, of it. It's basically a corrosive chemical that bubbles the paint off.
Example: http://www.kleanstrip.com/product/aircraft-paint-remover

It's not paint thinner.  Aircraft paint that,s applied in proper facilities like this is usually LPU / Imron or other 2-part works-like-epoxy coating.  Not least, because it's thinnest and lightest.   These dramatically transform into long polymers, so they are immune to their own solvent even 1 day into curing.  They are probably immune to retail "Aircraft Remover" too, but there are solvents that will attack them (and not aluminum, that's the real trick).

Stoddard solvent is a mild case of a paint thinner. More serious ones: Acetone, Nitrocellulose thinner, Methyl-Ethyl Ketone (MEK), Stabilised Tetrahydrofurane (THF)....

"it's actually not too different to other things that you paint." Except the paint used is very nasty stuff.

Mine was painted with a Polyurethane.  Really durable stuff. Gas, Oil, Stoddard Solvent do not touch it.  I don't know about it's nastiness.  http://annexpaint.com/index.php?main_page=product_info&products_id=111 "DuPont Imron Industrial Strength® is the next generation of Imron technology. Based upon patented DuPont formulations and resin technology, Imron® Industrial Strength is the fastest Imron yet, providing the "Wet Look that Lasts" with the lowest environmental impact. Imron Industrial Strength can be purchased in Gloss, Semi gloss, Satin or Flat."

fuel costs a lot [citation needed]. For all its wonderful properties (huge energy density, liquid in standard atmosphereric conditions, "freely" available in the ground) petroleum is actually dirt cheap. Try to power a 777 with fuel cells or li-ion batteries. First, see if it's possible at all. Then, take a look at how much it would cost.

Eric, I feel you've missed the point entirely. I didn't say jet fuel does not have currently unbeatable energy density, I said it costs a lot. Which it does. It's the single largest operating cost for airlines. Here's a citation: https://www.iata.org/whatwedo/Documents/economics/Airline_Labour_Cost_Share_Feb2010.pdf

Commercial airlines burn 100 billion gallons of fuel every year. I do hope it's a large operating cost for them. And it's not because fuel costs a lot, but quite simply because they burn 150 000 olympic swimming pools every year.

Ok, I guess we'll have to agree to disagree on how we determine what is a high cost item for airlines. But when you need to pay for a operating cost that can increase in price like this, just today, I believe it's a high cost item. I'll happily accept, there is currently no other technology available that could provide a better solution.

1000 lbs? Why do they bother painting them at all then? (other than the company logo)

In addition to the chemical method in Simon's answer, there are mechanical methods, like bead blasting. This method was introduced in the 80s by airforces concerned with the volume of chemical waste generated by their maintenance facilities.

It essentially consists of using compressed air to project fine plastic particles against the painted part at high speed. These abrade the paint away mechanically and can be recycled a few times before they break down too much and become ineffective. Glass particles can also be used for more heavy duty blasting, but these need more careful procedures to avoid damaging the substrate, since they are much harder than plastic.
Abrasive blasting not only removes paint, but also dirt, corrosion and even anodic coatings, with enough passes.
Whether it has any advantages over chemical stripping, depends on the specific case. Industry regulations change across time and space, and waste plastic dust might be more problematic than waste chemicals in some places, but not others. Also, the size of the parts to be stripped and the kind of training required for the operators play a significant role in choosing one method over another.

Baking Soda blasting is another method for mechanical removal.   https://www.youtube.com/watch?v=lub0D1pX_xo

@CrossRoads same principle, different blasting agent.

Not to be a smart-ass, but I think the correct answer is "in accordance with the airframe manufacturer's instructions."
Aircraft are generally given a corrosion protective layer (or passivated) at the time of manufacture that usually gives them a green color before they are painted.  For this reason, unpainted planes are sometimes called "green" planes.  Historically the treatment was usually a zinc chromate primer, but that is highly toxic and I doubt anybody still uses it on new planes.  I suspect some of the more modern treatments add green pigments just to give the green planes the expected look, but I don't actually know that.
Following manufacturer instruction on whether and how to use chemical strippers or mechanical removal of paint is important to not damage the protective layer in ways not expected by the manufacturer.  Some treatments require parts to be dipped in a chemical bath before assembly, so if you remove or damage that treatment layer, you're not likely to be able to restore the corrosion protection to an as-new status.  If you remove the protection and replace it with your own in a way not specifically approved by the manufacturer, your plane no longer is in full compliance with the type certificate and you've become something of a test pilot.
TL;DR: Don't do stuff to planes that isn't approved by the manufacturer or a supplemental type certificate applicable to your specific plane.

Stripped planes are taken down to bare aluminim. The AL is then washed, acid etched (something like a mild vinegar), alodyne applied, then primer (the green color), then paint.  The stripper doesn't know to stop at the primer level.  This was mine after the alodyne stage, before primer  http://www.crossroadsfencing.com/airplane/painting%20pics/IMG_0311.JPG

@CrossRoads Reminds me of a DeLorean :-) but I'm afraid it lacks the Flux Capacitor.

Well, that and stainless steel :)

Yes, @CrossRoads, but the look is awesome!

The green layer is just a temporary protection that gets stripped before the aircraft is painted.

I appreciate people sharing their experience with ways (some) planes are stripped, but you still only repaint aircraft in ways approved by the manufacturer.  I've done work for a manufacturer that feels quite strongly that the treatment on its planes should not be removed by stripper and that, because stripper doesn't know when to stop, the paint on its planes should only be removed mechanically.  Maybe you can get equivalent protection, but when you modify an aircraft in a way contrary to manufacturer instructions and don't have an STC, you don't really have a properly certified aircraft.

There are other methods in addition to the chemical and mechanical ones already mentioned in other answers. In some cases, paint is removed from aircraft using a laser.
Here's a video I found from the US Air Force that demonstrates the process:

F16, 25 hours for 2 robots.  C130, 75 hours for 4 robots.  Bet a Cessna would be pricey, if one could get time at an AF base to have it done.


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What is a Virtual Window in an aircraft?
I heard about Virtual Windows in the Dubai show, but I didn't really got it. What is it?
In a demo, when they opened the shields, I could just see the ground handling before taxing.
Search engines only gave me a patent, but I would rather learn about it laconically.
PS: Found in a triple seven.

I found a video where an english guy mentions them, but he doesn't seem to have a clue about their functionality.

@mins I disagree, we have plenty of questions about passenger accommodations.

I remember reading at one point the reason for this is that windows are difficult to build structurally and add a lot of weight to the aircraft. If the fuselage can just be an aluminum tube, that gives you better structural stability at a lighter weight. People probably feel too claustrophobic without windows, but a camera is a good compromise.

Does it show a virtual blue screen of death?

@Collin exactly what I was thinking. mins I started writing my question to the travel.se, but then thought it would better fit this site. Koyovis, not yet. ;)

They are basically window-shaped screens, displaying a feed from a camera so the middle aisle suits (where the alternative is a wall) passengers can enjoy the "view".

The most interesting thing to me are the virtual windows. First Class passengers in the middle suite will have a set of “windows” like everyone else, only theirs will show images from an outside camera.

https://travelupdate.boardingarea.com/virtual-windows-emirates/

Where is the camera pointed to?

@gsamaras outside, I suppose :) Probably to the side of the aircraft so the view is of an actual window.

Then what's the point? ;) I am thinking of something like the A380's camera view that the passenger can view on screen at the back of the front seat, where he can choose which view to be displayed! Thanks DeepSpace.

@gsamaras I think it will be pretty awkward to watch a front-looking feed from a "window". I'm sure it can make some people sick :)

@gsamaras Also, it is for the middle aisle suits. So the alternative is a wall.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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Could turbine or compressor stages of a jet engine be switched off to improve fuel efficiency?
Active fuel management is a technology developed by General Motors, which is used to improve engine efficiency in the times when the engine is operating under loads which are considerably less than the rated load, as shown in this link. This technology exploits the property of piston engines where some of the cylinders are turned OFF while only few of them work, and hence improving the overall efficiency of the engine. Can a similar technique be employed on an aircraft's engines, where some of the turbine stages (Compressor or Turbine) are switched off in order to improve the performance efficiency of the engine?

I don't think your analogy works. A car is powered by multiple identical, indivisible units (cylinders) and the power management system turns some of those off to conserve fuel. A plane is also powered by multiple identical, indivisible units (engines) so the analogous control mechanism would be to turn off some of those units (shut down an engine or two), not to somehow turn off parts of the units.

First of all, a compressor stage is not turbine's equivalent of a cylinder. This would be the combustor (aka flame holder).

The second issue is that reciprocating engine's cylinder uses very specific amount of fuel per cycle. Use too much or not enough and you get burn problems. In a car you also have very tight coupling of engine to the wheels: speed of X requires Y rpm which means Z fuel consumption (gearbox helps a bit, but just a bit). You can't dial down the power by reducing to any rpm you like. This problem does not exists on an aircraft: almost every rpm works at any speed (because jet exhaust is always faster than IAS). You can simply dial down the RPM, no need of partial shutdown of the engine.

You cannot "switch off" a stage of a turbine engine.
As seen elsewhere jet engines are a single block mechanically locked together: all the stages (compressor AND turbine) connected to the same shaft. If the shaft turns, all connected stages turn with it.
You can have designs with multiple shafts, but this increases the complexity (design and maintenance) heavily.
Even if we assume for a moment that you could have 1 shaft per stage, stopping one of these would be generally a bad idea.
For acoustic reasons the number of blades on the stationary part of the stage and those on the rotary part must be prime to each other (example: 37 blades on the stationary side and 39 on the rotary one); this means that when the rotary part stops you cannot align all the blades with the stationary ones, creating drag and losses within the engine, thus reducing the efficiency.

How would efficiency of a Jet Engine change, if we assume for a second that its a possibility, to stop a few stages(turn them into free instead of locked)?

You would still decrease the efficiency: compressor stages are the ones actually pulling the aircraft forward (you would then produce less thrust*) and the turbine stages are the ones extracting energy from the exahust.
*: you could even risk having the flame going upstream if you stop too many compressor stages and not having enough pressure at the combustion chamber inlet.

Lets say that we have an engine where the stages are attached to the shaft by some mechanism (which is a black box). This mechanism has the ability to turn to free and locked state. How would efficiency of a Jet Engine change, if we assume for a second that its a possibility, to stop a few stages(turn them into free instead of locked)?

Stopping individual cylinders in Active Fuel Management reduces the fuel burn, because otherwise a volume of air & fuel is needed for each revolution.  A jet engine doesn't have this fixed displacement problem; the fuel flow can just be reduced (within limits).  Perhaps you could let some turbine or compressor discs in the engine freewheel by adding extra clutches, but I suspect that would be far too complex mechanically, as well as add drag inside the engine...

More to the point. Additional stages increase Carnot efficiency by more closely approximating adiabatic expansion. The ideal jet engine has infinite stages (obviously not ideal from a manufacturing perspective), as at that limit, we get adiabatic expansion. There is no equivalent in an ICE, as ICEs do not have staged PV cycles.

Can it be done?
Yes
Has it been done?
Yes
Wait, what?! Where what how?
The Pratt and Whitney J58 was designed to allow partial shutdown of the compressor. It does this by placing a distinctive spike in front of the compressor assembly.
However the purpose of the transition to ramjet that is distinctive of the J58 was to allow it to avoid overheating the turbine during supersonic flight, where the increased inlet velocity translated to additional heating of the air.
However this does not increase the efficiency of the jet engine at all.
Overall you actually want as many stages as possible for subsonic flight. This is because multiple stages allow the gas to compress/expand more adiabatically, leading to better Carnot efficiency.

Very interesting - I thought the sr71 spikes were only for reducing airflow through the engine.

+1. I thought I knew the answer (it does not make sense) but I learned it is possible, and SR71 did that, for reasons linked. Thank you!

I can hardly agree. the PW-J58, as shown in the wiki page you linked, simply reduced the airflow to the turbojet duct. In addition The gas generator RPM was kept at 100% to maintain maximum thrust., hardly "switched off".

Short answer: No.
Longer answer: Jet engines are designed with multiple compressor and turbine discs mechanically attached to a single shaft, called a spool. Usually, there are 2 (or sometimes 3) of these spools within the engine, due to the need of the high pressure compressor and the main intake fan to spin at different speeds. Each spool spins freely and is driven by the compressed air in the engine core being pushed through the turbine stages attached to that spool.
Diagram of a Turbofan Jet Engine

Source: Wikipedia
There is no way to "shut down" a particular spool. As long as the pressure in the engine core is higher than the pressure behind the nozzle, the turbines will spin and drive the spool. If you detach either one of the turbine stages or one of the compressor stages from a spool such that it 'freewheels,' the turbine discs will likely overspeed due to decreased load. Additionally, an undriven compressor stage would experience compressor stall, which is essentially an aerodynamic stall of the blades of the compressor stage.

Finally, this is entirely unneeded for a couple of reasons:
First, aside from the problems it would cause, there would be nothing to gain from shutting down a compressor stage. As Andy correctly mentioned in a comment, jet engines do not have a constant fuel burn per revolution, unlike piston engines. If a jet engine doesn't need to produce as much power, it can simply inject less fuel in the combustion chamber. As the pressure in the combustion chamber drops, the spools will spin down accordingly on their own (due to less pressure driving the turbine stages.)
Second, the power output profiles of jet aircraft operation are nothing like those of a car. For a car, high engine power is usually used only in brief spurts for acceleration and cruise uses a small fraction of that amount of power. In a jet airplane, on the other hand, the engines will be operated at a rather high percentage of their maximum RPMs for most of the flight. This is because additional power allows them to fly higher, which actually increases efficiency. See the answers to the previous question How far can a 777 fly with just one engine at altitude? Unlike a car, significantly reducing the power during cruise flight actually reduces the fuel efficiency of an airliner.

"In a jet airplane, on the other hand, the engines will be operated near their maximum performance for most of the flight." That is certainly not true in civil aviation. The thrust in cruise is typically around 25% of the maximum takeoff thrust. I think the answer in link on "flying on one engine" seems somewhat confused.

@alephzero Thrust or RPMs? Thrust will be lower for the same RPMs due to less dense air (as that answer mentions.) I'll edit my answer to make clear that I mean RPMs here, not thrust.

If you extend the idea of "switch off" a bit, this is already done in several different ways.
Surveillance aircraft may be designed to loiter over their target area with some engines shut down completely. That is not just a matter of shutting down the engines - for example if you are going to loiter at high altitude for several hours at temperatures below -50C, you are likely to need special systems to heat the oil in the shut-down engines, to avoid damage when you restart them.
Many jet engines contain variable stator vanes in the compressors, which are automatically adjusted to improve the efficiency under different working conditions.
In multi-shaft engines, the relative speeds of the different shafts changes depending on the working conditions. That is more efficient that forcing all the compressor and turbine stages to run at the same speed on a single shaft. In a multi-shaft turbofan, the bypass ratio (i.e. the fraction of the air being compressed in the core engine and used for combustion, rather than just being blown by the fan to generate thrust) will also change.

Fuel efficiency is not improved by shutting off stages of a compressor or turbine. Fuel efficiency is a function of overall pressure ratio, reduce this and efficiency is reduced.


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When does a turbine need to go to maintenance?
I'm wondering what the limiting maintenance factors for engines, for example of an A320, are. Of course this is something that is different from one engine manufacturer to another and especially from engine type to another.
But what rules are there for regular, operation driven, maintenance?
Please consider engines of any type, used for a mid-sized plane like the A320 on commercial passenger flights.

This is all defined by the engine manufacturer, and there are multiple checks from simple oil and fluid changes all the way through full tear-downs.

Whenever the manufacturer, governing administrative body (FAA, etc), or operator require or decide it needs to in accordance with approved maintenance data and programs, monitoring programs, and inspections.

This is a very broad question, but if we limit ourselves to just high bypass turbofans, such as the CFM56 or LEAP-1A used on the A320, and limit "maintenance" to mean major maintenance that requires the engine to be removed from the wing, then the primary driver is typically the total number of flights.  Depending on the engine, it would be removed from the wing for a complete teardown, inspection, and rebuild perhaps every 5,000 - 10,000 flights (typical lifetime of the engine could be between 30,000 and 50,000 flights). Many major components are limited by low cycle fatigue (LCF) driven by thermal stress, so the cold-hot-cold cycle of a flight is what drives the maintence interval, more so than the total flight hours.  i.e. a 1 hour flight and a 12 hour flight are pretty similar in how much they wear out the components.

Thank you for your answer. Would it matter if a plane is e.g. 20minutes on the ground or 1h? Would that have any impact on maintenance cycles? I guess 20 minutes would not let the engines cool down as much as 1h and thus thermal stress would be "different".

20 min versus 60 min shutdown does make some difference to LCF life, but it's not huge.  Even just idle-takeoff-idle-takeoff (i.e. leave the engine running and never shutdown) induces a significant thermal stress due to the large temperature difference between idle and takeoff.


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Why don't B747s start takeoffs with full throttle?
Why does the 747 start takeoff with partial power and increase to full throttle later down the runway, when the A380 for example starts on full?

Source
This is not the same question as:

Is it possible that derated thrust takeoffs are safer than normal takeoffs?
Why don't airliners use full throttle on takeoff?

Regarding the video, keep in mind it’s taken with telephoto lens, so distance and speed of sound play a role in judging engine spoolup versus aircraft movement.

Also, the last major airline I worked with flying both last generation Airbus and Boeing aircraft, the takeoff procedures differed in so far as on the Airbus, brakes were released after thrust was stabilized at takeoff thrust, while on the Boeing throttle levers were advanced after brake release only. I never checked whether that was „our“ or the manufacturer‘s procedure, though.

When I was flying RJs, we would "stand the levers up", put them more or less vertical, which would give roughly low 70s% N1, wait for rpm to stabilize, then to TOGA.  That was the manufacturer's procedure.  If the runway was long, we would do it while starting the roll.  If the runway was short, we'd hold brakes until going to TOGA.

Just as a matter of information, as best I remember, on 747-200 aircraft, with JT9D-7Q engines and possibly earlier, if you stood on the brakes and brought the thrust levers to max takeoff power, the aircraft may start moving depending on your weight, the runway surface, and tire condition.

Side note: the A380 (or at least the RR Trent 900 equipping half of them) does not "start on full." Setting the throttles at TOGA while stationary only gives you about 80% power, rising to 100% only when speed becomes > 30 kt - I believe that is in order to increase the surge margin at low speed.

I can't give a 747 specific answer, but generally, on some engines it's desirable to let the engines stabilize at a moderate power setting, with the N1 equalized there, before advancing them to TOGA thrust. It helps to make sure the engines will all get to TO thrust at the same time, which is important to avoid yawing motions early in the roll.  The crew may hold the brakes and do it, not releasing brakes until the move to TOGA, or they may do it on the roll, which is probably what you were seeing.
There may also be limitations in the event of strong crosswinds against going to TOGA while stopped with the wind blowing from the side beyond a certain angle and above a certain speed, requiring that kind of rolling takeoff procedure (to minimize flow disruptions to which a particular engine may be sensitive).

Mentour Pilot talks about this in his video. The answer is Stabilization.
It takes an engine several seconds to spool up from idle to TO/GA. That's long enough that the engines don't get there at the same time. The difference can be enough to make asymmetrical thrust yaw the airplane on a slick runway.
Whereas, spooling up from mid-thrust to TO/GA happens very quickly, and so the time of differential thrust is too short to matter.
The time from idle to mid-thrust is most of the total time to TO/GA.  So they command mid-thrust, wait for both engines to catch up and equalize, then punch it.
They can't correct with rudder because it's ineffectual at low airspeed. They can't correct with differential braking because dragging brakes only works if you're moving.

This is a throwback to the old piston engine planes which would run up the engines and wait to see they all stabilize, perform properly and are equal. They find out about carb problems or fouled plugs before they are rolling down the runway.

+1 for a novice, an excellent break down.

Typically you run the engines to 60% N1 or so, then do a final sweep of the gauges for abnormalities prior to advancing to either maximum rated thrust or a lower pre determined rating.  It’s a means to verify everything works correctly one final time before committing to the takeoff roll.

Some engine types on the 747 are not capable of running at the maximum N1 (fan) speed with no forward speed to increase the air flow into the engine, especially at low altitudes and low temperatures.
You don't want to push the engine to the limit of the operating envelope and then have a gust of cross-wind that causes a compressor surge by disrupting the inlet air flow, until you have enough forward speed to prevent that sort of event from happening.
In other words, the engine is at maximum power for the operating conditions it is in, but it is not operating at the maximum RPM the fan is designed for.

Can you add a source for the N1 info? That would make this a really good answer

Rolling take-off..recommended practice if the runway is long enough as its easier on the airframe and also on the pax.
Standing on the brakes and running up to take-off power is only done on shorter runways. As the 747s mostly operate from bigger airports you would not normally see this.
If you've never experienced it and don't know whats happening it can be a bit disturbing as the noise and vibration increases a lot and there's a lot of initial acceleration when the pilot gets off the brakes. The last few I've been on were on smaller aircraft (a 737 and an ATR 72).. exciting to say the least!
Anilv

Another reason is foreign object debris (FOD), which is easily picked up by the outboard engines. This can be avoided by delaying the spool up to full thrust.

It's not an interceptor/air superiority fighter that needs to be up in the air 10 minutes ago nor is it taking off from an aircraft carrier which has a limited amount of runway length so you need a catapult (steam atm mostly but electromagnetic ones are being developed (and I think they are deployed on the USN's newest carriers)).
For other missions taking of with the afterburner (if you have one) and engine(s) at max isn't the most efficient way.


text:
Should I connect the AR6203 COM radio to the GMA324 audio panel using symmetric or asymmetric wiring?
I have this little project to change the Audiopanel and COM to GMA342, GNS430 and Becker AR6203. Airplane is a Piper 28-181.
I would like to know if I have to connect the AR6203 to GMA342 in symmetrical or asymmetrical wiring?
As far as I have researched it, I would say it is symmetric.
Is it a good idea to ground the audio shields at aircraft gnd/power gnd?

Are you doing this under an STC? You should have detailed information with the STC documents for those pieces of equipment.

I have all manuals, but this question seems to be trivial and nobody is answering it.  I just want to have the best possible audio wiring.

Since you're talking about a DC power system, chassis ground and power ground should be the same. So the power ground is commonly used for grounding shields. The question is: should you ground one end of the shields or both?
The purpose of the shields on the audio connections is to prevent induced audio frequency noise. To do that, the shields must have at least one ground point. RF engineers I've worked with will explain that the best solution is to have the shields grounded at both ends if the units at both ends are properly grounded and bonded. That's a big if, especially in general aviation avionics where slide-in mounting trays are used.
While the connections may be good when you install them, over time the connections can degrade and resistances increase. When that happens the "grounds" at the connected units are no longer at equal potential which can induce current flow through the shields. This 'ground loop' can induce a lot of noise into the lines.
Most installers I've worked with recommend terminating the shields only at one end thus eliminating any possibility of a ground loop. The key to this method is making sure any 'gap' necessary in the shield at the open end connector is as small as possible while still ensuring it doesn't make a connection. The small gaps aren't a big concern here as you're dealing with audio frequencies.


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Do military jets' radar jammers block their own radar? And, if not, why not?
Will a noise jammer block the fighter's own radar? If I have understood it, a noise jammer, e.g., a barrage jammer, will emit a noise signal across a wide frequency band. Won't this make it hard to interpret its own radar "hits"?
I and a buddy are trying to make a more advanced Mech game where we want to model the ECM war a bit more. So we are trying to learn :).

If you are emitting RF, you can be seen.  There are two ways to emit RF: 1. Transmit (or leak) a RF signal, and 2. Reflect a RF signal.
A jamming device emits (usually) high amounts of RF, with the general idea that the receiver of someone's radar unit will be desensed or otherwise overwhelmed by the signal.  Like putting a multicolored sun into a small dark room.
So with multiple receivers (as in multi-static radar) a jamming aircraft can normally be rather precisely located (assuming omnidirectional uniformity of the jamming signal).
When noise jamming, your aircraft may not broadcast on, near or on harmonics of a given frequency within a temporal frame of when you are emitting on that frequency, so your receiver has the opportunity to detect returns. More importantly, your noise emitter may drop power and your radar receiver may have cans (well, cavities) tuned to protect the sensitivity of your radar receiver when expecting a return signal.
There are many books on radar technology, but I believe EW102 covers radar, deceptions, noise jammers and other techniques in a manner that most mildly technical people can read and understand.  There are other books, but I use that series in an Electronic Warfare course I teach, and they are reasonably current. The open literature is rich with advances in jamming and other stealth methodologies that have advanced tremendously in the last 50 years.

The use of multi-static arrays or constellations adds complexity to a solution to the source of the wideband noise.  Such jamming is not typically run in a continuous mode in today's environment, and when used intermittently, is against an imminent threat, where the objective is very near term.  The idea is that the threat (eg missile) is run out before a solution can be obtained. Regardless, there are many different types of jamming, with applications in different scenarios. No one technique works universally.

@Notts90, a multicolored sun is an expression used to indicate a very bright emitter, which has many different frequencies (colors).  RF is radio frequency and generally refers to energy emitted in the radio frequency spectra.  For example the emissions of a transponder is RF. The emissions of radar are RF, and even the emissions of a jammer are RF.  In these three examples, each RF source has normally increasing ERP or effective radiated power.

@mongo what do you mean by EW102? What other books are there to read more about this topic?

@mike - EW 102 a second course in electronic warfare:
http://hollis.harvard.edu/HVD:everything:TN_skillsoftbke00000562. Intro to Modern EW is also good: http://hollis.harvard.edu/HVD:everything:TN_doaj_soai_doaj_org_article_cd12637a967c43a49d98b657d75d1197

@HephaestusAetnaean has it right.  Adamy has 4 books up to EW104. We use them in EW courses.

That's not the nature of how ECM works.
Here's a primer on basic electromagnetic countermeasures as was used during the Vietnam War.

Since ECM, or radar jamming, works by analyzing incoming radar energy, identifying it as a hostile emanation and the transmitting a counterfeit signal, the system quickly filters out friendly radar systems and does not duplicate their signals

Thank you. I had found that video and saw through it. Do most of the fighter planes use Deception Jamming? I had found this article ECM that mentions both forms. And it mentions Frequency-hopping as a common counter-countermeasure to deception jamming.
Noise jamming seems "safer", in the seance that you are actually always jamming, to an degree. But i will drop the point if all fighters do indeed use deceptive jamming :). I mean the video, while good, is a bit old.

Noise jammers will either have a filters to block out the frequency used by your own radars or there will be a "blanking" circuit to temporarily stop the noise jamming for a brief time to your radar operate.
Noise jammers are not as effective as they used to be. Back when radar had mechanically rotating antennas and relatively slow gating, the constant amount of noise prevented the radar from determining the direction or distance.
Most modern radars can easily distinguish noise jamming and ignore it. Also there are many weapons that will actually home in on the jamming signal since it is continuous.
Deception jamming is far more effective again modern radars, but there is a constant battle between Electronic counter measures (ECM) and Electronic Counter Counter measures (ECCM). so better radars need better jammers to counteract them.


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Why does Jet A currently cost roughly the same as 100LL?
I thought Jet A was substantially cheaper than 100LL but I recently looked at the prices throughout my area, and they are both priced at approximately $5.50 per gallon. I've never flown an aircraft that uses Jet A so I've never really paid attention, but I could have sworn that it was much cheaper than the leaded 100LL.
I can't find any articles or information online as to why Jet A is as expensive as 100LL. Avgas or 100LL is a specialty fuel and the only leaded fuel that is still made, so that explains why it is expensive, but Jet A is ubiquitous and produced in large quantity.
This previous question suggests the same thing that I'm saying, that Jet-A is cheaper because 100LL is a specialty fuel produced in small quantity, and Jet-A is widely available, etc. So, what has changed in the last 2 years?  It can't just be supply and demand.

Why can't it just be (local) supply and demand?

Taxation can distort the apparent price of fuel. Airlines can reclaim much of the fuel tax they pay on international flights.

Is it possible that Jet-A has been subjected to the same sort of low sulfur regulations that has made diesel almost as expensive as gasoline for cars?

@Sean there doesn't seem to have been any major disruptions in supply, and on the demand side, if anything, the groundings of the 737 Max have slightly reduced demand. But I'm not an industry insider so these are just superficial observations. I'm hoping to hear from someone who has actual knowledge of this issue. Also, Its not just local, I looked at prices across the country on sky vector and it appears to be wide spread.


text:
How is ATFM handled in the USA?
In my answer to this question, I describe how calculated takeoff times (CTOT) are used as a tool in European air traffic flow management to prevent overload and maximize capacity. I expect the ATFM system used in the USA to be quite similar, but I'm sure there are technical differences. I am hoping someone can provide a similar answer, detailing ATFM procedures in the USA.

original question:
Air traffic flow management (ATFM) is a service established with the objective of contributing to a safe, orderly and expeditious flow of air traffic by ensuring that ATC capacity is utilized to the maximum extent possible and that the traffic volume is compatible with the capacities declared by the appropriate ATS authority.
In Europe, air traffic flow and capacity management (ATFCM - notice the additional C) is handled by EUROCONTROL.
Each air navigation service provider (ANSP) is responsible for declaring the capacity of their ATC sectors in terms of a maximum number of movements that can be safely handled in given time intervals.
All IFR flightplans in Europe are processed centrally by the Integrated Initial Flight Plan Processing System (IFPS). If, based on the flightplans, it is calculated that capacity within a sector will be exceeded, flights might be rerouted or level capped, or they receive ground delay (a slot time).
This system works very well, and ensures an efficient and safe flow of air traffic within Europe. However, flights originating outside of Europe cannot be processed in the same way. For example, flights departing outside of Europe will not receive any slot times, which makes the system inflexible, since these flights still have to be taken into consideration, but cannot be adjusted the same way other flights can.
This has made me wonder, why is it not possible to simply link the European system with similar systems around the world, to create a global ATFM network? Specifically, I am interested in how ATFM works in the USA. I would like to identify the main differences between the European system and the system in the USA, with the goal of understanding what prevents these systems from working together.

It is a rather broad question, but it's well thought out and explained.

The problem with working together on a global scale or even trans-Atlantic is the long time and distance between. Flow control at least in the U.S. (and I'm sure elsewhere) is more short-term (1-2 hours out), mainly based around airport acceptance rates (AAR) which can change hourly or even more frequently for example because of runway configuration changes, or weather or visibility changes. There is also short-term projected sector saturation issues, and short-term sudden localized things like weather buildups that can come and go.
That means for trans-oceanic flights you can't effectively implement departure metering (the main tool in the U.S. for flow control) or ground stops because you can't predict 5-10 hours in advance the traffic level and acceptance rate at the destination airport. It's much more effective to wait until they're back in radar coverage and closer time-wise to the destination when flow control calculations will be more accurate, and controllers can achieve miles-in-trail spacing requirements with quick radar vectoring. Over the ocean, outside of radar coverage, significantly adjusting in-trail spacing is more difficult because you really only have speed adjustments which are limited because of the narrow aircraft envelopes at high altitudes.
For situations where there will need to be long-term flow control (such as, the only other runway is suddenly closed and will be indefinitely), we already do have a manual process to implement flow restrictions trans-oceanic, by each facility passing restrictions to adjacent facilities, on and on up the chain.  For example, Shanwick can tell Gander we need 10 minutes all aircraft all tracks landing EGLL, Gander tells Boston 12 minutes in trail, Boston coordinates with U.S. command center, etc to ensure Boston doesn't get overwhelmed with EGLL-bound aircraft. Those kinds of things happen very rarely though, so it's probably not worth connecting our different automation/flow control systems together and instead just keep handling it manually on a case by case basis.
(Source: I'm a former FAA controller and worked in flow control/Traffic Management Unit for several years).

Thanks for the interesting insight! So if I understand it correctly, Eurocontrol works on a significantly longer scale? They even have a strategic level, which is D-7.

Your question is rather broad, so I'll just say that there are efforts to harmonize the systems and point you to the resources.
The FAA management of air traffic is going through an evolutionary program called NextGen.  There is a large amount of information covering the program here.
The one document that would likely address most of your questions it the NextGen/SESAR State of Harmonization.


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What is meant by "Fox Two"?
Numerous Movies, Video Games, and TV shows featuring fighter pilots depict the pilots calling out "Fox Two" on the radio as they fire a missile.
The transmission (as depicted, I'm not sure about IRL) frequently does not include the aircraft identifier (tailnumber or callsign). (but sometimes an aircraft ID is included)
What does this signify? Why is it important? And why is the term "Fox Two" rather than any other variation of "Missile Fired"/"Missile Away"?
How are other pilots meant to respond when they hear "Fox Two" on the radio?

Fox codes are used by NATO military aircraft to designate a release of an air-to-air munition, generally missiles.
Fox One is a semi-active radar guided missile, for example the AIM-7 Sparrow. This type of missile requires the radar of the launching aircraft to guide it to its target.
Fox Two is an infrared-guided missile, for example the AIM-9 Sidewinder. This missile is "fire and forget".
Fox Three is an active radar guided missile, for example the AIM-120 AMRAAM. This missile has its own radar to track the target; it is "fire and forget".
Fox Four is guns. Previously this was Fox Three.
You can find all the acronyms and brevity codes in the Field Manual 1-02-1 on page 33 of the PDF.

Good to know there are other kinds of "Foxes", that aren't frequently shown in fiction.  However, why does it need to be called out at all?  What're you supposed to do when you hear that from your fellow pilots? For AAR purposes, wouldn't the flight recorder and other data sources show what weapon was fired at what time at which target?

@abelenky - "What're you supposed to do when you hear that from your fellow pilots?" Don't get between the missile and its intended target. Otherwise, it may lock on to YOU.

@WPNSGuy: Scenes from "Top Gun: Maverick" not withstanding, it is virtually impossible for a friendly craft to maneuver fast enough to get in front of an un-intended missile even deliberately, much less accidentally.  It is also the responsibility of the Pilot firing the missile to fire only when the target path is clear of friendlies.

Seeing as there have been documented air to air kills from 28km, Turkish F-16 v Syrian MiG....doesn't seem to unlikely to me. 28km is about 30 seconds flight time for an AMRAAM. That sounds like a lot of space and time.

@WPNSGuy "How do friendly-fire incidents happen?" sounds like a separate question.

@abelenky In movies it's Fox 2 because that's what you would fire in a dogfight--and in the movies it's a dogfight for drama.  Radar guided missiles are typically used in reasonably long range engagements that are blips on the radar--not much for the silver screen.

@abelenky I wouldn't say it's impossible--if you're already near the target getting in the way of the missile is certainly possible.

One great reason to announce the launch of a missile and the type is so that your wing and flight and command are aware of your remaining weapons load. They also would all know the number of bandits and approximate range of engagement. This keeps the situational awareness up for everyone, which means everyone can make informed decisions. "Guns guns guns" is also called when guns are used. Combined with "splash one" for kills, the radio alone can be an effective situational awareness tool.

@abelenky on the 'why do weapon launch brevity words exist in general' is that often launches are made to another orders, so the codeword is your 'I have complied with your command, now doing the next thing'. In the world of equipment from the lowest bidder can also mean 'all my technology worked, backup weapons can be reprioritized'. Finally it also means 'any command to NOT kill this target is now irrelevant'.

There's also an unofficial joke that "Fox 4" is using the aircraft itself as a weapon (ref: Google Groups, Reddit)

And it seems to me that "Fox" stands for the letter "F" (maybe in turn for "fire/firing"). So the number following is the category of what has being launched/fired.

I'm fairly sure most modern (at least NATO standard missiles) have IFF capabilities no?

@U.Windl Specifically "Fox" is short for "Foxtrot", which is the NATO phoenetic code for the letter "F", and yes it does mean "Fire".  This should probably be added in the answer, but you can see it on the Wikipedia link under the word "Fox".

@abelenky I seem to recall at least one incident of an aircraft shooting itself. With guns. So, friendly fire might not be as farfetched of a possibility as you'd think.

@reirab It was a F11F Tiger, in 1956, during a live-fire cannon test in a Mach 1 dive. The bullets were slowed down by drag and the plane was going so fast that it shot itself. The pilot had to ditch. It happened with a F14 in 1973 and a F16 in 2009.

@Benson_YoureFired If the pilots were allowed to continue flying, I wonder whether their crews painted silhouettes of their previous aircraft on their next one?

A heat seeker won't "ping" the defender's radar, and since the launch is simulated you won't see a smoke trail either. In a training situation saying "Fox 2" on the radio tells the defender that there is a simulated missile in the air, and cues them to simulate popping flares and maneuvering to defend against the missile.

But "Fox Two" is also used for actual launches, not just simulated ones.

It is?  Do you know this for a fact?  (you reference "Numerous Movies, Video Games, and TV shows...")

@Michael Hall - Yes, it is used in real munitions release as well. From Wiki "Fox is a brevity code used by NATO pilots to signal the simulated or actual release of an air-to-air munition or other combat function."  Also, from personal discussions with USAF pilots over the years.

"It is? Do you know this for a fact?" I'm referencing the document linked by @Benson_YoureFired in his answer, which appears to be an authoritative document.

I stand corrected, thanks!  Something in my distant memory recalls hearing that you wouldn't announce your attack to the enemy, but I can also see some benefit for AWACS, wingman, etc.

I certainly hope in a real battle, your communications are fully encrypted and the enemy cannot hear your call.  You certainly wouldn't make the call on UNICOM or CTAF! (hah)

Indeed that would be true!

@abelenky unless you are lying to throw your enemy off (ha!)

@Michael, on more than one occasion I have seen your comments and thought "I don't remember saying that..."!

@MichaelHall I have done that on more than one occasion with various other Michaels, but not when they have a last name attached :)


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Can the Kinzhal really fly 2,000km? Or can the ROCKS (at least its warhead)? Is there a way to tell fact from fiction for ALBM ranges?
Published ALBM (air launched ballistic missile) ranges are all over the place. For the Russian Kinzhal, wikipedia gives "an estimated range of 460–480 km". But another site (which was the first hit in Google for me) gives "between 1,500km and 2,000km".
Likewise for the Israeli ROCKS, FT gives 2,000km range. There is not much in the way published ranges elsewhere for this ALBM, but an Indian magazine (reporting on India's tests of that missile) says "well over 250 kilometres", which is not exactly a contradiction, but does look like underselling by a fair amount relative to the other claim.
Yet another page says "The range of ROCKS is less than 300 km". This might be for the export variant (to India), though.
Is there a way to tell fact from fiction for ALBM ranges? Of course, a lot depends on launching altitude, I suppose. Can one roughly estimate the max range, e.g. by assuming that a certain portion of the missile is fuel, and by knowing the external dimensions, which are perhaps less easy to fudge? ICBMs tend to be physically bigger than IRBMs and so forth for that reason, I assume.

I see that at least the burnout altitude seems somewhat easy to estimate https://www.armscontrol.ru/course/articles/primer.pdf (p. 4) based on the propellant and payload mass, assuming a specific propellant, but I suppose it's somewhat harder to guesstimate the thrust. Anyhow, even a range equation is given (eq. 13 on p. 7) based on the burnout altitude and velocity (ans some orientation). I guess the hardest to guesstimate among these is the thrust?

I see that ultimately that author assumes an exhaust velocity of 2.4 km/s for pretty much everything from Scuds to Minuteman.

@mins: none of that is what I'm asking here though.

@mins: fair enough, that bit probably does matter. FWTW, I see wikipedia gives "Mach 5.9" burn out velocity for the Iskander. I'm guessing the extra speed for the Kinzhal is mostly due to being launched at altitude, but who knows.

You can use an energy balance estimation to check if the claims match energy required and available. Energy available is calculated from the missile's propellant mass fraction and launch parameters.
A ballistic missile is assumed to get almost no lift and lose little to drag. Its most efficient flight path is a ballistic arc. The missile's delta-V ($\Delta V$) must satisfy two conditions:

$V = V_0 + \Delta V > V_\text{max}$
$V^2 / g > R$ where

$V_0$ is the launch platform's speed, $\Delta V$ is the missile's own energy, $g$ is acceleration due to gravity ($9.8\approx 10$ ) and $R$ is range in meters.
The two positive energy inputs come from air launch and propellant, calculated as $V_\text{aircraft} + I_\text{sp} g \ln(M_f/M_e)$ respectively, per the Tsiolkovsky equation -- where $I_\text{sp}$ is the specific impulse of the propellant, and $M_f$ and $M_e$ are the full and empty masses of the rockets. An empty Kinzhal probably weighs $\sim0.1 M_f+M_\text{guidance}+M_\text{warhead} \approx  0.1\times 4\,300+100+500 \approx 1030$ kg, giving it a $M_f/M_e \approx 4$. $I_\text{sp}$ for solid propellants is usually assumed at 240 seconds, but can be up to 295 seconds.
Solving for the Kinzhal:

$V_\text{max} = 10 \times 320 = 3,200$ m/s
$V^2 / 10 > 2\,000\,000$ , therefore $V > 4\,472$ m/s
Air launch at Mach 2, at 10 km: $V_0\approx 670$ m/s
Propellant impulse $= 2500 \ln(4) \approx 3\,460$ m/s
Total $V = 4\,130$ m/s

Conclusion: Using a conservative energy estimate, with the same weight, engine, and warhead weight as the Iskander, the highest claims of 2,000-3,000 km are not plausible. The missiles' best-case range can't be more than 1,700 km.
Furthermore, Mach 2 is pretty fast for a launch platform. A subsonic launch would further reduce range to $R=(280+3460)^2 \approx 1\,400$ km. An even faster launch would improve range, but solving for $R=2\,000$ km gives a $V_0$ of Mach 3, which might be possible for the MiG, but goes contrary to the stated 3,000 km with the Mach 2 Tu-22M3.
There are three possibilities:

The claimed range of 2,000 km originally included the combat radius of the launch platform. This is consistent with 3,000 km for the much longer-ranged Tu-22. But the missile itself only covers 1,000-1,700 km.
It's only loosely based on the Iskander, and uses a more modern propellant. It would take an Isp of 280 s to reach 2,000 km from Mach 2.
A combination of 1 and 2: the missile is slightly improved, but its range of 2,000 km is an impractical scenario for a top-speed MiG-31 zoom climb, and 1,000-1,500 km operationally.

The reports of Kinzhal's interception say it was nothing special, basically falling at about 1,240 m/s, which is consistent with an older boost-only rocket. Any upgrade would've likely bumped it to boost-sustain type, which don't lose so much speed near the end. Given that, I lean towards the first option, but the third is plausible as well.
But its range is almost certainly over 1,000 km, given how far they have struck, and also considering that air launch is a substantial boost to a ballistic missile's range.
As for the Rafael ROCKS, it's impossible to check without more specs. But overall, I'd expect option 1 for it as well. Israel's opponents have next to no air forces or defenses, their region of interest is geographically tight, and their military doctrine tends to favor payload to begin with. They don't have much of a use case for a 2,000 km missile.

I have a stone somewhere around with a range of 7.000 km (including the launch plattform range).

You say the stated range is not plausible, while calculating "only" 1700 km. However, the question stated an estimation of 460–480 km which is well under it, and the highest estimation was "between 1,500km and 2,000km", and 1700 is indeed between those numbers. So what exactly is not plausible?

@vsz 2,000 km or 3,000 as stated in wiki isn't plausible. But 1,500 is indeed possible.

Where is the $V_\text{max} = 10 \times 320 = 3,200$ m/s coming from?
And Mach 2 at 10 km is ~590 m/s

@ROIMaison I've added a little delta-V to compensate for the gravity drag, saved by the "free" 10 km. Vmax comes from Mach 10 times 320 (which is admittedly a semi-random number)


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What is the difference between types of propeller?
I have been noticing almost every Multirotor vehicle uses a single thin double-bladed propellor on each axis. And yet clearly, there are some that do not fit the norm.

Can someone explain what the effect of each of these changes would do to a normal quadrocopter?
1) Adding more Propellors.
2) Adding more Blades on each Propellor.
3) Replacing all Blades with Wider Blades.
4) Making the angle of each blade steeper.
5) Replacing propellors with Contra-rotating propellers
6) Spinning Propellors faster

Welcome to Aviation.SE. This seems to be quite a lot of points for a single question, please consider splitting these points in more than one question.

Good reading about quadcopter desing: Build A Quadcopter From Scratch and for motors: How to choose Motor and Propeller for Quadcopter and Multicopter.

As for splitting this into multiple questions I'm not sure how exactly I would do that. I guess in general I was just asking how propellor design effects a quad, but that is just as broad.

There should be two parameters you should know about:

Blade loading: The amount of force per unit of area a blade is creating. Like with a wing, you can formulate a lift coefficient, a dimensionless number which removes the influence of size, air density and speed. Ideally, this number should be between 0.5 and 0.7, so the propeller makes best use of its blade area.
Advance ratio, which is the ratio between the circumference of the propeller disc and the height it would screw itself up into the air in one rotation. Increasing the blade angle would directly increase this advance ratio, for example.

Now you should be able to guess the answers to your questions:

Adding more propellers: Will distribute the load over more propellers and helps if blade loading was too high, but makes matters worse if blade loading was low already.
Adding more blades: See 1.
Replacing blades with wider blades: See 1.
Making the angle of all blades steeper: If you run the prop at a lower speed, your blade loading will go up and thrust will be the same (if you don't mess up the flow over the blades by changing the angle). If you run the prop at a higher speed, blade loading will go up; again until the flow cannot cope with the angle anymore. This is similar to stalling a wing. Changing the blade angle is the preferred means of adjusting the prop to different flight speeds in airplanes.
Adding a second, contra-rotating prop is like adding another sets of props (see 1), but helps to reduce swirl losses. If blade loading was at a proper value before, halving blade loading will create more losses than reducing swirl losses. You add contra-rotating props only if your blade loading was high already.
Spinning propellers faster will create more thrust but also more losses. If your thrust is not sufficient, it is better to increase prop diameter (a parameter you forgot to include).